Production of fibers



United States Patent 3,]l2l,43 PRGDUCTION 9F FEBERS Karl F. Braeuninger,Ferguson, and John A. lllasltiewicz,

St. Louis, Mo assignors to The Dow Chemical Company, Midland, Mich acorporation of Delaware Filed May 16, 1960, Ser. No. 29,492

. Claims. ((31. 29-412) This invention relates to a method and devicefor producing fibers of a light metal material whose shear strength isless than its tensile yield strength. It more particularly concerns amethod and apparatus for fiberizing magnesium and its alloys.

The formation of fiberized magnesium and magnesiumbase alloys heretoforehas been accomplished by extruding a mixture of particulated magnesiumor a magnesiumbase alloy with cupric acetate or an organic blue dye asdisclosed in US. Patents 2,657,746, and 2,701,636. Bundles of easilyseparable fibers wherein the individual fibers each are from about 0.001to about 0.003 inch thick and of varying lengths result from theprocesses disclosed in these references. Such fibers exhibit a hightensile strength which makes them useful as fibrous fillers, as forexample, for rubber reinforcement and the like. Additionally, thesesmall diameter fibers have a large surface area to weight ratio whichrenders them especially useful in flashlight work, for example, or inother applications where the ability of the material to undergo rapidoxidation may advantageously be utilized.

There are, however, certain disadvantages inherent in the production offibers by these known methods, e.g., (1) the fibers so-produced are ofnon-uniform length and cross section, (2) a residual film of thenon-metallic mix ingredients or by-products thereof may be deposited onthe fibers during the extrusion and (3) the processes are relativelyexpensive. Now, unexpectedly it has been found that by using the methodof the present invention, fibers of substantially uniform cross sectionand length can be obtained by a unique metal shaving operation whereinmagnesium or a magnesium-base alloy is pulled or pus-i ed through ashaving die whose cutting edge is not perpendicular to the direction ofmaterial travel.

It is a principal object of the present invention to provide a methodfor the production of fibers of substantially uniform cross-section andlength. It is a further object of the invention to providemagnesium-base metal fibers which, as produced, are substantially freefrom undesirable surface coatings. It is another object of thisinvention to provide an inexpensive method of producing magnesium andmagnesium-base alloy fibers. An additional object of the invention is toprovide fibers of a preselected length and cross-section.

Numerous other objects and advantages of the inventlon of the presentapplication will become apparent from the detailed specificationpresented hereinafter and by referring to the accompanying drawings, inwhich similar characters of reference represent corresponding parts ineach of several views.

In the drawings:

FIGURE 1 is a plan of a shaving die assembly useful for producing fibersby the method of this invention showing drawstock and fibers.

FIGURE 2 is a sectional View taken along line 22 of FIGURE 1.

FIGURE 3 is a front elevation of the having die of FIGURE 1.

FEGURE 4 is an enlarged sectional view of the die orifice and die cavityof the shaving die of FIGURE 3 through the upper and lower long sides ofthis orifice.

FIGURE 5 is a top view of a drawstock material which has been scored attwo places parallel to its longitudinal axis, i.e. along the length ofthe drawstoek.

3,121,943 Patented Feb. 25, 1964 ice FIGURE 6 is an end view of thescored drawstock of FIGURE 5.

The shaving die assembly 115 shown in the drawings and illustrative of auseful means of producing fibers is a modified conventional drawing dieassembly and is composed of a rectangular prismatic die plate holder 16having a cavity 17 and an attached die plate 18. The die plate 18 can beattached to the die plate holder 16 by a variety of convenient means,e.g. silver soldering, common screws, clamp, welding, fitted into apocket in the die holder etc. as is known and apparent to one skilled inthe art. The leading or forward face 19 of the die plate 18 is not madeparallel to the face 20 of the die plate holder 16, but is at an angle21 to it. The die plate 18 has a substantially rectangularly shaped dieorifice 22 approximately centered in this plate. This orifice 22 has itslong axis extending in a horizontal direction across the die plate 13.The two cutting edges 23 of this die orifice 22 are the foremost pointof short lands 24 ground at an angle of to the face 19 of the die plate18. The two short ends of the orifice 22 are not cutting edges but arerounded or otherwise shaped to keep the drawstock from skewing sidewaysduring the drawing operation. The remaining length of the die cavity 25behind the lands 24 is machined at an angle on all walls 26 so that thiscavity widens outwardly as it passes through the die plate 18. The dieplate and die holder assembly are placed so that the die cavity 25 opensinto the cavity 17 of the die plate holder.

The angle 21 between the leading fac 19 of the die plate 13 and the faceof the die plate holder 16 is from about 1 to about 10 with an angle ofabout 5 preferred.

The die orifice 22 shown in the illustrated embodiment is rectangular inshape. However, it is understood that this die orifice can be any of avariety of geometric shapes, e.g., trapezoidal, hexagonal, crescent,hemicircular and the like with the only limitations being (1) that therebe two angular junctions of plane edges with a given cutting edge (2)that the shear angle between the cutting edges of the die orifice andthe material being fiberized be from about 1 to about 10 and (3) thematerial of construction of the die cutting edge be of sufficienthardness and strength rating to satisfactorily cut the fibers from thedrawstock.

In practicing the method of this invention, a shaving die assembly 15having a substantially rectangular orifice 22; and an angle 21 of about5 etween the die plate face 19 and die holder face 2% is mounted in aconventional drawbench apparatus (not shown) in the same positionnormally occupied by the drawing die of such apparatus. A light metaldrawstock material 27 is selected for fiberizing whose shear strength isless than its tensile yield strength, for example; magnesium, wroughtmagnesium alloys such as the ASTM designated A231 (nominal composition 3percent aluminum, 0.4 percent manganese, 1 percent zinc, balancemagnesium), AZ63 (nominal composition 6 percent aluminum, 0.18 percentmanganese, 3

ercent zinc, balance magnesium), A280 (nominal composition 8.5 percentaluminum, 0.18 percent manganese, 0.5 percent Zinc, balance magnesium),I-IM21A (nominal composition 0.6 percent manganese, 2 percent thorium,balance magnesium), HK31A (nominal composition 3 percent thorium, 0.7percent Zirconium, balance magnesium), and ZK60A (nominal composition5.5 percent zinc, 0.6 percent zirconium, balance magnesium) and thelike, wrought aluminum alloys such as the Aluminum Associationdesignated 5052 (nominal composition 2.2-2.8 per cent magnesium,0.15-0.35 percent chromium, balance aluminum), 5056 (nominal composition4.5-5.6 percent magnesium, 0.05-0.20 percent manganese, 0.05-0.20percent chromium, balance aluminum), 6061 (nominal composition, 0.4-0.8percent silicon, 0.15-0.40 percent copper, 0.08-12 percent magnesium,0.150.35 percent chromium, balance aluminum), 6063 (nominal composition0.20.6 percent silicon, 0.450.9 percent magnesium, balance aluminum) andthe like and other materials of similar characteristics. The termmagnesium alloys as used herein means metallic materials containing atleast 75 percent magnesium, aluminum alloys as used herein meansmetallic materials containing at least 75 percent alumi num. Thedrawstoek 27 is formed to have the same rectangular shape as the dieorifice 22 but will be thicker than the opening 28 between the cuttingedges 2323 of the orifice 22 and will be somewhat narrower than thewidth of this orifice. To illustrate, with a rectangular orifice havinga 0.100 inch opening between the two 3 inch long horizontal cuttingedges, a magnesium or magnesiumbase drawstock of from about 0.102 to0.120 inch thickness by about 2.90 inches or less in width will beutilized. The drawstock is pulled or pushed horizontally through theshaving die assembly in the same manner as is used in conventionaldrawing operations. The line of force applied to the material is normalto the vertical plane of the leading face 20 of the die plate holder 16whereby a shear angle of is obtained. The substantially uniform fibers29 released from the drawstock surface then may be collected.

Fibers resulting from the shaving operation are substantially uniformlysquare in cross section both along the length of each fiber as well asare consistently uniform from fiber to fiber. The cross section width ofthe fiber is a function of, and is essentially equal to, the depth ofthe shaving cut taken from the drawstoek surface in the drawingoperation. The length of the fiber is determined by the width of the dieorifice cutting edges and/or that of the material being shaved. Usingthe present method with those materials whose shear strength is lessthan their tensile strength, fibers are sheared from the width of thedrawstock which fibers have their longest length substantially equal tothe width of this drawstock; i.e. a large number of fibers are formedsubstantially parallel to the cutting edges of the die orifice as thedrawstock is pulled through the die rather than one continuous foil orroll being removed from the length of the drawstock as might beexpected.

The rate of drawing is not critical and is dependent only on the powerand drawspeed of the drawbench facility utilized.

It is understood that in this method a multiplicity of such fiberizingdie assemblies can be mounted in series each having the die platemounted concentrically about the geometric centerline of the perimeterof the drawstock. Further the die orifice of each die plate is of thesame shape but each succeeding die orifice has a thinner opening betweenthe cutting edges than its preceding neighbor. If desired, one shavingdie can be prepared which has infinite adjustments of the cutting edgesin towards the centerline of the material being shaved so that after thedrawstock has been passed through the die orifice and the finishedfibers have been released from the surface the die orifice opening canbe made thinner to accommodate a succeeding pass of the material throughthe same die. Alternatively, a die can be prepared having only onecutting edge. The material can be repeatedly passed through this dieusing a backing member, for example, shim stock, to compensate for thesurface metal removal in each pass. These above listed procedures can befollowed on a given drawstock material until the cross-sectional area ofthe material being shaved becomes too small to withstand the tensileforces required to move the stock through the tool.

Fibers of varying preselected lengths can be prepared by this method byscoring the drawstock parallel to the longitudinal axis of the material.The depth of the score mark, or serration, is at least equal to thethickness of the fiber producing cut and is made prior to pulling thematerial through the shaving die. Spaced serrations 4 across a drawstockwill determine the ultimate length of the finished fiber.

Additionally, it will be recognized that the serrating and fiberizingoperations of this method can be carried out either independently orsimultaneously.

The following examples will illustrate further the present invention butare not meant to be construed as limiting it thereto.

Example 1 A rectangular orificed (0.124 inch thick by 5 inch wide)shaving die assembly having a die plate face-die holder face angle ofabout 5 was mounted into a conventional drawbench. The die orifice hadcutting edges along both the top and bottom of its 5 inch width. Two 10feet lengths of 0.064 inch thick by about 5 inches wide of ASTMdesignated AZ31 magnesium alloy sheet nominal composition 3 percentaluminum, 1 percent zinc and balance magnesium, were placed back to backand pulled through the shaving die in a horizontal direction and withthe drawing force normal to the perpendicular face of the leading edgeof the die plate holder thereby giving a shear angle of about 5. Therate of shaving was about feet per minute. Magnesium alloy fibers fromboth the top and bottom cutting edges, which were substantially 0.002inch on a side and about 5 inches long formed at the entrance face ofthe die and were removed.

As a control, the die plate was positioned so that the leading facecontaining the cutting edges of the die orifice was parallel to thevertical faces of the die holder. A second set of similar AZ31 plateswere pulled through the die orifice, the shear angle now being 0. Theshavings produced were in the form of a continuous foil of about 0.002inch thickness, and about 5 inches wide.

Example 2 A shaving die assembly similar to that used in Example 1,except that the leading face of the die plate made a shear angle ofabout 2 with the line of force applied to the drawstock, was mounted inthe drawbench apparatus. The die orifice was rectangular and its openingmeasured 0.200 inch thick by 4 inches wide. A five foot length ofmagnesium drawstock 0.220 inch thick by about 4 inches wide was serratedto a depth of .01 inch along its length on both sides of the 4 inchstock using a conventional scoring tool. Three serrations were made,which divided the width of the stock into four substantially equalsections. The bar stock was then drawn through the shaving die at aboutfeet per minute whereby substantially square uniform shavings of about.010 inch on a side and 1 inch in length were released from both sidesof the stock by the cutting edge of the die orifice.

Example 3 A shaving die assembly and drawbench apparatus as in Example1, except that the leading face of the die plate made a shear angle ofabout 8 with the line of force applied to the drawstock, was mounted inthe drawbench apparatus. An AZ31 wrought magnesium alloy drawstock 12feet long and 0.134 inch thick by about 5 inches wide was drawn throughthe shaving die at about feet per minute, and the .005 inch square byabout 5 inches long fibers, which formed on both sides of the stock atthe die face entrances, were removed.

Various modifications can be made in the present invention withoutdeparting from the spirit or scope thereof for it is understood that welimit ourselves only as defined in the appended claims.

We claim:

1. A method for producing fibers of a light metal material whose shearstrength is less than its tensile yield strength which comprises;

(a) providing a shaving die assembly, said shaving die assembly having arectangular die orifice, and a light metal material whose shear strengthis less than its tensile strength, said light metal material having thesame shape as said die orifice but being of a preselected thicknessgreater than the opening of said die orifice,

|(b) passing said light metal through said die orifice of said shavingdie assembly at a shear angle between said die orifice and the line offorce applied to said metal of from about 1 to about 10 thereby toremove as fibers by each cutting edge of said die orifice a pre-selectedamount of from about 0.001 inch to about 0.010 inch of surface of saidlight metal, and

(c) shaving from said light metal material fibers having a lengthsubstantially the same as the width of said light metal material.

2. The method of prducing fibers as defined in claim 1 wherein the lightmetal is magnesium and alloys thereof and the shear angle between thedie orifice and the line of force applied in passing the metal throughsaid orifice is about 5.

3. The method of producing fibers as defined in claim 1 wherein awrought aluminum alloy is utilized as fiberizing material.

4. A method :for producing fibers of magnesium and alloys thereof whichcomprises;

(a) providing a shaving die assembly mounted in a 5 drawbench apparatus,said shaving die assembly having a rectangular die orifice, and adrawstock material selected from the group consisting of magnesium andmagnesium based alloys, said drawstock material having the same shape assaid die orifice but of a preselected thickness greater than the openingof said die orifice,

(b) drawing said drawstock material through said die orifice at a shearangle between said die orifice and the line of force applied in drawingsaid metal through said orifice of from about 1 to about 10 thereby toremove as fibers by each cutting edge of said die orifice a preselectedamount of from about 0.001 inch to about 0.010 inch of surface of saiddrawstock, and

(a) shaving from said drawstock material fibers having a lengthsubstantially the same as the width of said light metal material.

5. The method as defined in claim 4, and including the step of serratingthe faces of the drawstock exposed to the cutting edges of the dieorifice along the length of the longitudinal axis of said drawstock,these serrations being of substantially the same depth as thepreselected depth of cut taken from said faces by said cutting edges ofsaid die orifice thereby to prepare fibers the length of which aresubstantially the same as the width of the drawstock between saidserrations.

References (fitted in the file of this patent UNITED STATES PATENTS644,978 Greaser Mar. 6, 1900 1,009,688 Peterson et a1. Nov. 21, 19112,233,928 Weaver Mar. 4, 1941 2,323,700 Bailey July 6, 1943 2,694,400Brock Nov. 16, 1954

1. A METHOD FOR PRODUCING FIBERS OF A LIGHT METAL MATERIAL WHOSE SHEARSTRENGTH IS LESS THAN ITS TENSILE YIELD STRENGTH WHICH COMPRISES; (A)PROVIDING A SHAVING DIE ASSEMBLY, SAID SHAVING DIE ASSEMBLY HAVING ARECTANGULAR DIE ORIFICE, AND A LIGHT METAL MATERIAL WHOSE SHEAR STRENGTHIS LESS THAN ITS TENSILE STRENGTH, SAID LIGHT METAL MATERIAL HAVING THESAME SHAPE AS SAID DIE ORIFICE BUT BEING OF A PRESELECTED THICKNESSGREATER THAN THE OPENING OF SAID DIE ORIFICE, (B) PASSING SAID LIGHTMETAL THROUGH SAID DIE ORIFICE OF SAID SHAVING DIE ASSEMBLY AT A SHEARANGLE BETWEEN SAID DIE ORIFICE AND THE LINE OF FORCE APPLIED TO SAIDMETAL OF FROM ABOUT 1* TO ABOUT 10* THEREBY TO REMOVE AS FIBERS BY EACHCUTTING EDGE OF SAID DIE ORIFICE A PRE-SELECTED AMOUNT OF FROM ABOUT0.001 INCH TO ABOUT 0.010 INCH OF SURFACE OF SAID LIGHT METAL, AND (C)SHAVING FROM SAID LIGHT METAL MATERIAL FIBERS HAVING A LENGTHSUBSTANTIALLY THE SAME AS THE WIDTH OF SAID LIGHT METAL MATERIAL.